## Cp vs Cv

Jesse Kuehn 1B
Posts: 40
Joined: Wed Nov 14, 2018 12:23 am

### Cp vs Cv

How do we know when to use Cv or Cp? I know one is constant volume and one is constant volume but for a problem where it looks like both are constant, how can we tell which one to use?

Chem_Mod
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### Re: Cp vs Cv

There will always be enough information to deduce which to use.

Sophia Ding 1B
Posts: 62
Joined: Fri Sep 28, 2018 12:16 am

### Re: Cp vs Cv

I've found that most problems we deal with have to do with temperature change; you will then use Cv because it is the pressure that is changing with the system rather than the volume (even if there is volume expansion occuring but that will be taken into account with a different equation). You will use Cp generally when the problem itself explicitly states that there is a constant pressure with the ideal gas.

Ethan Breaux 2F
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Joined: Sat Sep 29, 2018 12:16 am

### Re: Cp vs Cv

Cp = Constant Pressure
Cv = Constant Volume

Tuong Nguyen 2I
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### Re: Cp vs Cv

Going off of what Sophia said, unless there is something in the problem that explicitly states that pressure is constant, you will always use the Cv constant because we can't assume that pressure is constant when nothing within the problem mentions pressure.

Shibhon_Shepard
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Joined: Wed Nov 15, 2017 3:04 am

### Re: Cp vs Cv

There are some times that they give you the C or heat capacity and you would just multiply this C by the number of moles.

Jack Hewitt 2H
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Joined: Fri Sep 28, 2018 12:27 am

### Re: Cp vs Cv

The problem should give you enough information to determine which to use.

jlinwashington1B
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Joined: Fri Sep 28, 2018 12:22 am

### Re: Cp vs Cv

Constant volume, and constant pressure... The problem should contain enough information to determine which one you should use.